1. Field of the Invention
The present invention relates to a liquid crystal display device, and more particularly to a liquid crystal display device which has a structure in which a gate signal is directly applied to a gate line by an integrated printed circuit board without any gate printed circuit board.
2. Description of the Related Art
A liquid crystal display device applies a voltage to a molecular arrangement of a liquid crystal to convert the molecular arrangement to another molecular arrangement. The liquid crystal display device converts the changes of the optical properties of liquid crystal cells which emits light according to the molecular arrangement, and uses the modulation of the light of the liquid crystal cells.
The liquid crystal display device includes a liquid crystal panel to which electrical signal are applied to determine whether the light has been passed. The liquid crystal panel is a passive light device, and a back light assembly for providing the liquid crystal display device with the light is attached to the rear surface of the liquid crystal panel. A source part for applying screen data to display the screen and a gate part for applying gate signals for driving the gate device of a thin film transistor of the liquid crystal panel are attached to the liquid crystal panel. An electrical signal is applied to the liquid crystal of the liquid crystal panel by applying a picture signal to the transistor of the liquid crystal panel through the source part and the gate part, and the light from the back light assembly is regulated to constitute a screen.
The method for connecting the liquid crystal panel to the source and gate driving IC is sorted into a COG (Chip-On Glass) type and a TAB (Tape Automated Bonding) type. According to the COG type, a driving IC of a semiconductor package type is directly mounted to the gate and data areas of the liquid crystal panel, to transfer the electrical signals to the liquid crystal panel. The driving IC uses an anisotropic conductive film, and is bonded to the liquid crystal panel.
According to the TAB type, the liquid crystal panel is directly connected to the printed circuit board by using a tape carrier package to which the driving IC is mounted. One end of the tape carrier package is connected to the liquid crystal panel, and the other end of the tape carrier package is connected to the printed circuit board. Then, the input wire of the carrier package is connected to the output pad of the printed circuit board by soldering or using an anisotropic conductive film.
Examples of the liquid crystal panel modules which use the tape carrier package are disclosed in U.S. Pat. No. 5,572,346 issued to Sakamoto et el. And U.S. Pat. No. 6,061,246 issued to Oh et el. The conventional TFT liquid crystal modules mainly use the tape carrier package to mount the driving IC.
Recently, LCD modules of various structures have been developed to slim the LCD module. Especially, considering the LCD modules are used in portable computers, the light weight of the LCD module is important. If the tape carrier package is applied to the LCD modules, the flexibility is insufficient. Therefore, a flexible circuit board is used in an LCD module. A COF (Chip On Film) method is used to mount the driving IC to the flexible circuit board. According to the COF method, a chip is mounted onto the printed circuit board by using a TAB.
Since the weight and the volume of the liquid crystal device is increased as the size of the screen becomes larger, an effort to reduce the area and the volume which is occupied by a portion except for the screen has been processed. For example, an U.S. patent application Ser. No. 09/551,404 which was filed on Apr. 17, 2000, is pending with USPTO and corresponds to Korean Patent Application No. 99-13650 discloses a liquid crystal display device which removes the gate printed circuit board which increases the thickness of the liquid crystal display panel.
A circuit of the gate portion of the liquid crystal display device is removed to reduce the volume and the weight of the liquid crystal display device. However, since the gate tape carrier package is bent towards the rear surface of the mold frame into which the liquid crystal display panel is received and is attached to the rear surface of the mold frame, the height of the liquid crystal display device is increased according to the position of the driving IC which is mounted to the gate tape carrier package.